. The main hypothesis to be tested in this proposal is that impairment of alveolar macrophage (AM) functions in AIDS may contribute to the frequency of opportunistic infections including cyrptococcosis. In particular, this proposal seeks to characterize protective responses of normal human alveolar macrophages (AM) to Cryptococcus neoformans and to determine how they may be impaired in AIDS. The work has been divided in several specific aims designed to study 1) the effects of C. neoformans on cytokine expression in AM, 2) the effect of AM-derived cytokines on the ability of AMs to phagocytize and kill C. neoformans, 3) the effects of HIV infection on AM function and ability to clear C. neoformans, and 4) the capacity of C. neoformans to induce HIV expression in AM.